1. Interactions of Neuropeptides on Acetylcholine (ACh) Release: Neuropeptides (calcitonin-gene related peptides, neuropeptide Y, tachykinins, vasoactive intestinal peptide/peptide histidine- isoleucine, bombesin/gastrin-releasing peptide and cholecystokinin-octapeptide) will be examined on myenteric and submucous plexus in terms of their ability to modulate release of ACh from cholinergic neurons. ACh will be measured by radiochemical and radioenzymatic methods. 2. Characterization of Galanin Inhibitory Action on Enteric Cholinergic Neurons: Inhibition by galanin of basal and neuro- peptide-evoked ACh release from myenteric plexus, submucous plexus neurons and from enzyme-dissociated myenteric ganglia will be examined. Comparisons will be made with inhibition of ACh release by somatostatin and opioid peptides. 3. Mechanism of Release of Substance P from Enteric Neurons: Basal, neuropeptide- and field-stimulated release of substance P from tissue preparations mentioned in Aim #2 will be determined by an enzyme-linked immunosorbent assay using a monoclonal anti-substance P antibody. 4. Characterization of Neuropeptide Receptors on GABAergic Neurons: Release of GABA by neuropeptide stimulation from enteric neurons will be measured by a radiochemical method. Specific antagonists will be used to characterize neuropeptide receptor sites on GABAergic neurons.